Telephone-exchange system.



H. G. WEBSTER. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG. 4, 1904.

930,51 3. Patented Aug. 10, 1909.

2 SHEETS-SHEET 1.

H. G. WEBSTER. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG. 4, 1904.

' Patented Aug. 10, 1909.

2 SHBETS-SHEET 2.

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TINTTEE STATES PATENT OFFTQE. HARRY G. WEBSTER, OF CHICAGO, ILLINOIS,ASSIGNOR TO MILO G. KELLOGG, OF CHICAGO,

v ILLINOIS.

TELEPHONE-EXGHANGE SYSTEM.

Specification of Letters Patent.

Patented Aug. 10, 1909.

Application filed August 4, 1904. Serial No. 219,14=.

To all whom it may concern:

Be it known that I, HARRY G. WEBSTER, a citizen of the United States,-and a resident of Chicago, county of Cook, and State of illinois, haveinvented certain new anduse- "till Improvements in Telephone-ExchangeSystems, of which the following is a full, clear, concise, and exactdescription, refer cnce being had to the accompanying drawings, forminga part of this specification.

invention relates to central battery telephone exchange systems in whichsubscribers lines extend from substations to an cxcl'iange, and arethere associated with cord connecting apparatus; the said cordconnecting apparatus including a supervisory signal or signals, whichare controlled jointly by the manipulations of the operator, and

the actuation of'the subscribers hook switch.

Systems of this character have been devised in which thesupervisorysignal is asmall incandescent lamp, its circuit being controlled by adifferentially wound relay having its two windings included in the twotalking strands of the cord circuit. In such systems it is necessarythat a line wire leading from one side of the central battery benormally connected to ground through a contact associated with thesubscribers hook switch, the ground connection being automaticallybroken when the telephone is taken for conversation. In other systemswhich have gone into use, the use of a ground at the subscribersstationis avoided by using two relays, one for each of the talk ing strands ofthe cord circuit; and in such systems the supervisory signal is in alocal circuit controlled by the joint action of the circuits is suchthat when the connecting.

plug is inserted into the jack ofan idle line a circuit will becompleted through one of the relay windings through which current willflow in a direction tending to weaken the magnetization in one pole ofthe magnet causing the armature to move to a position which will causethe dlsplay of the supervisory signal, which may be an indicatordirectly connected to the armature, or a lamp or mechanical signal in alocal circuit controlled by the. armature. When the line circuit isclosed at the subscribers station a second circuit will be completedthrough the other winding of the polarized elect-romagnormal positioneilacing the supervisory signal.

The arrangement which I have outlined may be embodied in a number ofdi'lierent constructions and will be more fully explained in thefollowing description.

In the accompanying drawings illustrating a preferred form of myinvention I have shown diagrammatically in Fig. 1, two completelinecircuits of the three wire type in association with cord connectingapparatus including such a polarized electromagnet as I havedescribed.In Fig. 2 I have indicated similar cord connecting apparatus associatedwith two different line circuits of the two wire type, one line circuitbeing that employing a cut-off relay and a separate signal controllingmagnet, and the other line circuit that in which a single relayassociated with the line causes the display of the line signal whenenergized to a limited eX- tent and causes its eiiacement when energizedto a greater extent.

Referring to Fig. 1, subscribers stations A. and l3 are provided withthe usual apparatus adapted for use with a central source of currentsupply, comprising a receiver 1' and a transmitter t, in a circuit whichstands normally opened at the contact of the hook switch it; the bell band condenser 0 being in permanent bridge of the line limbs. Undernormal conditions limbs 1 and 2 of the line extend to the central ofiiceand are there connected to the acks j, limb 1 being also carried throughthe windingof the line relay 8 to the'negative side of the centralbattery C; and limb 2 is carried through the contacts t6 ot' the cut-olfrelay to the positive or grounded side'of the central battery O. Thewinding of the cut-off relay 5 is of comparatively high resistance, andis interposed between the test pieces or thimbles 13 of the jacks andthe positive side ofthe battery C. The jacks are provided with tipcontact pieces 11 and sleeve contact pieces 12 and are so arranged thatwhen a connection plug is inserted an electrical connection isestablished between the sleeve springs 12 and the thimbles 13, throughthe sleeve contact piece of the plug. The cord connecting apparatusincludes an answering plug 2) and a calling plug 0, the plug tips 14 16being united by strands 18-2O and condenser d, and the plug sleeves 1517being united by strands 19-21 and condenser e. The usual listeningkey23, operators set 24, ringing key 25 and generator 26 are provided, andthe listening key is so arranged that the noninductive resistance 22 isbrought into circuit of strand 20 when the key is moved to the listeningposition. A supervisory relay 28 is associated with the answering plug,having a permanent magnet whose poles N-S serve normally to give acorresponding polarity to the armature 34:, and pole pieces tl42respectively, of the relay. A spring 36 and stop 35 are so arranged thatthe armature is held normally in the position shown in the drawing, butwhen actuated during the course of a connection it engages contact 38,completing the circuit of supervisory lamp 39. The relay cores areprovided with a winding 3031 associated with the tip strand of the cordand a second winding 3233 associated with the sleeve strand, and thesewindings are so connected that when connected with the battery 0 asshown, they will be in opposition or differentially'connected, and thewinding 30 31 is so proportioned as to produce a preponderating effectover winding 3233 when in circuit. A second supervisory relay 29 ofsimilar construction is associated with the calling plug 0, and controlsthe circuit of supervisory lamp 40. g

. Subscriber A in calling completes the circuit of relay 8 and batteryC, lighting the line lamp 9 in the usual manner. Upon the insertion ofthe answering plug 79 a circuit of battery C is completed throughwinding 3233 of relay 28 through strand'19 and plug sleeve 15 of thecord circuit thimble 13 of the jack and the winding of relay 5,

causing the actuation of the latter relay to break the normalconnections of the line to relay 8 and battery C. The plug sleeve 15being also in contact with sleeve spring 12 of the jack, another circuitis completed from this point through the line limbs and instrument tospring 11 of the jack, tip 14 and strand 18 of the cord and winding 303lof relay 28. It will be seen that at this time the current flow throughwinding 333 of the relay is greater than that through its opposingwinding, but as previously stated, the winding 3031 is so proportionedthat the magnetic eti'ect of the current traversing it is sutlicient toneutralize or overcome the eli'ect of the current in winding 32-33; andthe armature 34; thus remaining in its normal position, lamp 39 remainsunlighted. After learning from subscriber A with which line connectionis desired (in this case that of subscriber B) the operator tests in theusual manner, her

key being in the listening position. In case the line is idle the tip 16and thimble 13 will have the same potential and no effect will beproduced when they are brought in contact. if, however, the line werebusy, current would flow from the positive side of battery C throughrelay 29, strand 20, resistance 22, plug tip 16, thimble 13 and thencethrough the plug sleeve and circuit of the cord at the point where thebusy connection existed. This would produce a click in the operatorsreceiver in the Well-known manner, but on account of resistance 22,which at this time is in circuit with strand 20, and is of relativelyhigh resistance, the disturbaucein the circuit of the tested line wouldbe reduced to a minimum, the resistance 22 being provided for thispurpose. Upon finding that the line is idle the operator inserts hercalling plug 0 and rings in the usual manner. Upon the insertion of theplug a circuit of battery C is completed through winding 32-33 of relay29, strand 21, plug sleeve 17, thimble 13, and relay 5 of line B, thelatter relay being thus energized to break the normal connections of theline to relay 8 and battery C. lVhile ringing, the currentfrom generator26 serves to maintain relay 5 energized and thereby prevents the displayof the signal lamp 9, as will be understood. The adjustment of relay 29is such that the current which at this time flows through winding 3233,strengthens the normal magnetism of pole 41, and weakens that of pole 42to an extent sufficient to attract the armature 34 to pole 4-1 and closethe circuit of supervisory lamp 410 from battery C, through wire 62,armature 34: and contact 38, thus lighting the lamp. When subscriber Bresponds, completing the circuit of limbs 1 and 2, additional currentwill flow through winding 3233 of relay 29, and circuit will becompleted through line limbs 1 and 2, springs 11 and 12 of the jack, tip16 and strand 20 of the cord circuit and winding 30-31 of the relay. Onaccount of the relative proportions of the two windings the magneticeitect of the current through winding 30 31 equals or overcomes that ofthe current through winding 3233, thus restoring or increasing thepolarity of pole 42 and restoring or decreasing that of pole 41; thearmature 34 now returns to its normal position, extinguishing lamp 40,which indicates that subscriber B has answered. When either subscriberhangs up, the circuit through winding 30-31 being broken, the currentthrough winding 3233 will again cause theactuation of armature 34lighting lamp 39 or 40. W hen both lamps are lighted, constituting theusual disconnect signal, the operator removes the plugs, and the variousparts return to the normal position shown in the drawing.

Fig. 2 shows substantially the same'cord connecting apparatus as thatofFig. 1, but

is indicated in association with line circuits of different characters.The line circuit of subscriber D dififers from that of A. in Fig. 1, inthat the cut-off relay 44 is directly oonnected to. one side of thetalking circuit, but the thimblcs 46 ofthe acks 7c are not brought intodirect connection with line limb 1 until after the operation of thecutoff relay. In this case the subscriber D calls in the usual mannercompleting the circuit. of relay Sand lighting the signal lamp 9, bothbymeansof current from battery C. When the operator plugs in to answer,circuit is completed through winding 3233 ofthe relay 28 and throughcontact 43 of the jack and the windingof the cut-0d relay 44,causing'the operation of the latter. Upon the operation of i this relaythe normal battery connections of the llne limbs are broken, andcontacts 4748 of the relay are brought into engagement; thus completinga second circuit through relay 28, which includes the two line limbs andthe windings 3()31 of the relay, causing lamp 39 to remain unlighted, aswas described with regard to Fig. 1. The busy test is secured in thesame manner as previously described and when the operator of subscriberD, the cut-oii' relay 44 is energized during ringing by current frombattery C flowing through resistance 43 instead of by current from theringing generator 26. After the restoration of the ringing-key, thecut-ofi relay 44 is energized by current through winding 32-33 of relay29 as in the previous case and the armature 01" relay 29 is attracted tocause the illumination of supervisory lamp 40; which is extinguished assoon as the subscriber by answering com-- pletes the circuit throughwinding 3031 of the relay. As soon as the circuit through winding 3031of either supervisory relay is broken bykthe replacement of thesubscribers receiver, therelay armatures assume their normal position,lighting'their corre sponding supervisory lamps. It is thus seen thatthe operation of the signals is the same as that in the first figure.

Referring to the line circuit of subscriber E of Fig. 2, the relay 50associated with the the supervisory lamp unlighted.

character are now known and the present drawing is only a diagrammaticillustration of such a structure. Subscriber E in calling, completes acircuit or" battery C through winding 51 of the relay 50, thence throughcontacts57-56, through limbs 1 and 2 of theline and contacts 55-58, tothe positive or grounded side of the battery. The wind ing 51 has arelatively weak magnetic effect and" can only actuate armature contact53 which, engaging contact 54, completes the circuit of lamp 9 throughcontact pieces 5955, and 58, causing the illumination of the lamp. Whenthe operator plugs in to answer, a circuit is completed, which may betraced as follows :trom the negative side of the battery through winding3233 of the relay 28 associated with the plug p, through contact 46 ofthe ack, thence through winding 52 of relay 50, and back to the positiveor grounded side of the bat- .tery- This winding 52 having relativelygreat magnetic ett'ect, causes the actuation of the additional contactsof the relay; contacts 56. 57 are separated, disconnecting winding 51from the line; contacts 5558 and 59 are separated, disconnecting theline from its direct connection with the positive side of the battery,andopening the circuit of lamp 9extinguishing the same; and contacts55-60 are brought into engagement thus connecting thimble 46 directly tolimb 2 of the line. The circuit of the line limbs 1 and 2 being closedat E a circuit is now comeludes both windings of the supervisory reilay, and as previously described the arma plugs in to call on a linesimilar to that ture remains in its normal position, leaving The busytest is secured in the same manner as previously described; and when theringing key is actuated, a circuit of battery C being thus completedthrough resistance 43, thimble 46 and winding 52, the relay 50 isenergized to its greater extent and all of its contacts are actuated aspreviously described.

The circuit of the calling generator is completed from ground throughthe ringing key, contact 45 of the jack, the two limbs of the line,contacts 55-60 of the relay and throughwire 61 to the circuits of thebattery C and the ground or common return as in the previous cases. Uponthe restoration of the ringing key winding 3233 only of the relay 29 isin circuit, the armature of the -relayis consequently actuated and lamp40 lighted. Then the subscriber answers, circuit being then completedthrough both relay windmgs the armature assumes its normal osition extin'uishin the lam When a out out of circuit and the lamp relighted by theactuation of the relay armature. lVhen the connection is taken down allparts assume their normal position. While in Fig. 2 I have indicatedthat the calling plug and answering plug are associated with separatebatteries it will be understood that these may be one and the same.

lVherever in the following claims I have referred to the non-use of aline, it is to be understood that I am referring to that condition inwhich the telephone of the associated line is not in use, rather than tothe existence of a connection with said line at the central ofiice.

Wherever in the following claims I refer to the use of a line, it is tobe understood that I am referring to the conversational circuit beingestablished.

While I have illustrated the polarized supervisory relays as having twosplit windings and indicated a certain arrangement of permanent magnet,cores and armature it is obvious that relays of this character may bearranged in other ways and I therefore do not wish to limit myself toany particular construction. It will be also evident to those skilled inthe art that a cord circuit such as I have indicated may be associatedwith other line circuits without departing from the spirit of myinvention, and I therefore do not wish to be limited to the precisearrangement of apparatus and circuits shown, but claim .1. Thecombination in a telephone exchange system of a cord circuit adapted tomake connection with a telephone'line, a signal controllingelectromagnet associated therewith responsive to current in a circuitestablished by the connection of said cord circuit to the line, meansincluding a wind- 'ing for securing a greater energization of one poleof said electromagnet over the other during the non-use of the line tocause the display of a signal, and a second winding for securing adecreased energization of said first pole and an increased energizationof said second pole when the line is in use whereby the said signal iseifaced.

2. The combination in a telephone exchange system of a cord circuitadapted to make connection with a telephone line, a po larized signalcontrolling magnet associated therewith responsive to current in acircuit established by the connection of said cord circuit to the line,a winding for securing a greater energization of one pole of saidelectromagnet over the other during the non-use of the line to cause thedisplay of a signal, and a second winding for securing a decreasedenergization of said first pole and an increased energization of saidsecond pole when the line is in use whereby the said signal is eifaced.

3. The combination in a telephone exchange system of a signalcontrolling electromagnet having two windings associated with a cordcircuit and responsive to current therein when said cord circuit isunited to a telephone line, and a normally cfi'aced signal associatedwith said electromagnet, adapted to be displayed by the greaterenergization of one pole of the electromagnet over the second pole bycurrent through one only of said windings, and to be again effaced by asubstantially equal or greater energization of the said second pole as aresult of current through said second winding.

4. The combination in a telephone eX- so change system of a signalcontrolling elec- 1 tromagnet associated with a cord circuit andresponsive to current therein when said cord circuit is united to atelephone line, a normally efi'aced signal associated with saidelectromagnet, adapted to be displayed by the greater energization ofone pole of the electromagnet over the second pole, and to be againeffaced by a substantially equal or greater energization of the saidsecond pole, means including one energizing winding only for securingthe said energization only of the first pole of the electromagnet whenthe cord circuit is united to an idle line, and a second winding forsecuring said equal or greater energization of the second pole of theelectromagnet when the line is in use.

5. The combination in a telephone exchange system of a cord circuitadapted to make connection with a telephone line, a signal controllingelectromagnet associated therewith adapted to display a signal inresponse to the greater energization of one pole of the electro-magnetover the second pole, and to eiface said signal in response to asubstantially equal or greater energization of the said second pole,means including one energizing winding only for securing the saidenergization of said first pole when the line is not in use and the cordcircuit con- 11o nected thereto, and a second winding for securing theequal or greater encrgization of said second pole during the use of theline.

6. The combination in a telephone exchange system of a cord circuitadapted to make connection with a telephone line, a signal controllingelectromagnet having two windings associated therewith adapted todisplay a signal in response to the greater energization of one pole ofthe electromagnet over the second pole, and to eiface l said signal inresponse to a substantially equal or greater energization of the saidsecond pole, a circuit including one of said windings only controlled bythe operator for securing said energization of'said first pole, andmeans for securin the equal or greater energization of said second poleduring the use of the line by current through said second windin 7 Thecombination in a telephone exchange system of a cord circuit adapted tomake connection with a telephone line, a signal controllingelectroinagnet associated therewith adapted to display a signalinresponse to the greater energization of one pole of the electromagnetover the second pole and to efl ace said signal in response to asubstantially equal or greater energization' of the second pole, acircuitincluding one winding only of said signal controllingelectroinagnet controlled by the operator for securing said energizationof said first pole, and a circuit including a second winding controlledfrom a sub-station for securing said equal or greater energization ofsaid second pole.

8. The combination in a telephone exenergization of said second poleduring the use of the line. I a

9. The combination 111 a telephone ex change system of a cord circuitadapted to make connection with a telephone line, a polarized signalcontrolling electromagnet associated therewith adapted to display asignal when one pole is energized to a greater extent than the other andto eilace said signal when said second pole is energized to an equal orgreater extent than said first pole, a circuit including one windingonly of said polarized signal controlling electroinagnct, controlled bythe operator for securingsaid cnergizatiou of said first pole, and asecond winding for securing the equal or greater energization of saidsecond pole during the use of the line.

10. The combination in a telephone exchange system of a cord circuitadapted to make connection with a telephone line, a polarized signalcontrolling electromagnet, having two windings associated therewithadapted to display a signal when one pole is energized to a greaterextent than the other and to efiace said signal when said second pole isenergized to an equal or greater extent than said first pole, a circuitincluding one of said windings only controlled by the operator forsecuring said energization of said first pole, and a circuit includingsaid second winding controlled from a sub-station for securing the equalor greater energization of said second pole.

11.- The combination in a telephone exchange system of a telephone lineuniting a sub-station with the central ofiice, a switch at thesub-station for controlling the fiow of current over said line throughthe substation, a cord circuit and an associated signal controllingelectromagnet, said cord circuit being adapted to make connection withsaid line and to complete a circuit through one energizing winding onlyof said associated signal controlling electromagnet, means includingsaid winding only for securing an increased energization of one poleonly of said electro-magnet over a circuit controlled by the operatorwhereby the said magnet is caused to display its signal, and a secondwinding included in a circuit controlled by the sub-station switch forsecuring an equal or greater energization of the other pole of saidmagnet over the first mentioned pole whereby the said signal is etlaced.

12. The combination in a telephone exchange system of a telephone lineuniting a sub-station with a central oflice, a cord circuit adapted tomake connection with said line, a polarized signal controllingelectromagnet associated therewith having two windings and responsive tocurrent in one winding only to cause the display of a signal, but notresponsive to current in both windings, a circuit for the said onewinding only, local to the exchange and under the control ofthe'operator for causing the actuation of theelectromagnet and means underthe control of the subscriber for controlling an increased flow ofcurrent through both windings when the line is switched for conversation.

13. The combination in a telephone exchange system of a telephone lineuniting asub-station with a central office, a cord circuit adapted tomake connection with said line, a polarized signal controlling magnetassociated therewith having two windings and responsive to current inone winding only to cause the display of a signal, but not responsive tocurrent in both windings, a

circuit for the said one winding local to the exchange and under thecontrol of the operator for causing the actuation of the electromagnet,and means under control of the subscriber'for controlling a circuit ofboth windings when theline is switched for conversation.

14L-The combination in a telephone exchange system of a telephone lineuniting a sub-station with a central office, a cord circuit adapted tomake connection with said line, a polarized signal controlling magnethaving two opposing windings and responsive to current in one windingonly to cause the display of a signal but not responsive to current inboth windings, a circuit for the said one winding only local to theexchange and under the control of the operator for causing the actuationof the electromagnet, and means under control of the subscriber forcontrolling an increased flow of current through both windings when theline is switched for conversation;

15. The combination in a telephone ex change system of telephone lineuniting a sub-station with a central oiiice, a cord circuit adapted tomake connection with said line, a polarized signal controlling magnethaving two opposing windings and responsive to current in one windingonly to cause the display of a signal but not responsive to current inboth windings, a circuit for the said one winding local to the exchangeand under the control of the operator for causing the actuation of theelectromagnet, and means under control of the subscriber for controllinga circuit of both windings when the line is switched for conversation.

16. The combination in a telephone exchange system of a telephone lineuniting a sub-station with a central otfice, a cord circuit adapted tomake connection with said line, a polarized signal controlling magnethaving two opposing windings and responsive to current in onewindingonly to cause the display of a signal but not responsive to current inboth windings, means under control of the operator for completing acircuit through the said winding only, and means under control of thesubscriber for controlling a circuit of both windings when the line isswitched for conversation,

17. The combination in a telephone exchange system of a telephone lineuniting a sub-station with a central ofiice, a cord circuit adapted tomake connection with said line, a polarized signal controlling magnetassociated therewith having two opposing windings, one of lessermagnetic effect than the other, an armature for said magnet normallyengaging a stop and adapted to be only actuated from its normal positionto cause the display of a signal by current in the said lesser winding,means under the control of the operator for completing a circuit throughthe winding of lesser effect, and means under control of the subscriberfor completing a circuit through the other wind ing to cause theeffacement of said signal.

18. A telephone exchange system including telephone lines extending to acentral ofiice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, link circuits for uniting said lines for conversation,a source of cur rent associated with said link circuits and adapted tobe bridged across the line circuits when connected for. conversation, aconnection including resistance extending between one of said lineconductors of a connected telephone line and a return conductormaintained at a potential different from that pole of the source ofcurrent then connected to said line conductor, a polarized signalcontrolling electromagnet associated with said link circuit, having awinding included in circuit with said source of current and with saidresistance when said line is connected with said link circuit, whereby adifi erence in the relative polarization of the poles of saidelectromagnet in a certain direction is secured to cause the display ofits signal, and a second winding for said electromagnet in a circuitunder the control of the sub-station switch for destroying said relativedifference in polarization whereby said signal is etlaced.

19. A telephone exchange system including telephone lines extending to acentral oiiice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, link circuits for uniting said lines for conversation,a source of current associated with said link circuits and adapted to bebridged across the line circuits when connected for conversation, aconnection including resistance extending between one of said lineconductors of a connected telephone line and a return conductormaintained at a potential diii'erent from that pole of the source ofcurrent then connected to said line conductor and a polarized signalvcontrolling electron'lagnet having two windings associated with saidlink circuit, one

of said windings being adapted, when energized alone, to cause adifference in the relative polarization of the poles of saidelectromagnet in a certain direction to cause the display of its signal,and the other of said windings being adapted, when energized, to destroysaid diiierence of polarization whereby said signal is eiiaced.

20. A telephone exchange system including telephone lines extending to acentral ofiice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, link circuits for uniting said lines for conversation,a source of current associated with said link circuits and adapted to bebridged across the line circuits when connected for conversation, aconnection including resistance extending between one of said lineconductors of a connected telephone line and a return conductormaintained at a potential diti'erent from that pole of the source ofcurrent then connected to said line conductor, and a polarized signalcontrolling electromagnet having two windings associated with said linkcircuit, one of said windings being included in circuit with said sourceof current and with said resistance when said line is connected withsaid link circuit, and included also in circuit with said source ofcurrent and source of current then connected to said line with thesecond winding when the circuit of the telephone line is closed at thesubstation, whereby a difference in the relative polarization of thepoles of the said electroinagnet in a certain direction is secured bycurrent over the former path to cause the display of its signal, andwhereby said difference in polarization is destroyed by current oversaid latter path to etiace said signal.

21. A telephone exchange system includlllg telephone lines extending toa central oflice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors, atthe switchboard, link circuits for uniting,

said lines for conversation, a source of current associated withsaidlink circuits and adapted to be bridged across the linecircuits whenconnected for conversation, a connection including resistance extendingbe tween one of said line conductors of a connected telephone line and areturn conductor maintained at a potential different from that pole ofthe source of current then connected to said line conductor, a polarizedsignal controlling electromagnet associated with said link circuit,having a winding included in circuit with said source of current andwith said resistance when said line is conpoles of said electroinagnetin a certain di-;

rection is secured to cause the display of its signal, a second windingfor said electromagnet in a circuit under the control of the substationswitch for destroying said relative difference in polarization wherebysaid signal is efi aced, and a test circuit extending from said returnconductor through a signal producing device to the testing contact pieceof a plug, whereby,rwhen said testing contact piece ofthe plug isengaged with that contact piece of a spring jack connected with saidresistance, a flow of current will result through said test circuit itanother plug is inserted into another spring jack of the same line, andwhereby, when no connection exists with the line, no test indicationwill result. a V

22. A telephone exchange system including telephone lines extending to acentral oiiice, line conductors for extending said telephone lines tothe switchboard, spring jacksassociated with said line conductors at theswitchboard, link circuits for uniting said lines for conversation, asource of current associated with said link circuits and adapt-v ed tobe bridged across the line circuits when connected for conversation, aconnection including resistance extending between'one of said lineconductors, of a connected telephone line and a return conductormaintained at a potential diiierent froin that pole of the to cause a'diiii'erence in the-relative polarization of the poles of saidelectroniagnet in a certain directionto cause the display ot its signal,and the other of said windings being adapted, when energized, to destroysaid difference of polarization whereby said signal is eiiaced, and atest circuit extending from said return conductor through a signalproducing device to the testing contact piece of a plug, whereby, whensaid testing contact piece o'f he plug is engaged with that contactpiece of a spring jack connected with said resistance, a flow of currentwill result through said test circuit if another ping is inserted intoanother spring ack of the same line, and whereby, when no connectionexists with the line, notest indication will result.

23. A telephone exchange system including telephone lines extending to acentral otlic'e, line conductors for extending said tele phone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, link circuits for uniting said lines for conversation,a source of current associated with said iink circuits and adapted to bebridged across the line circuits when connected for conversation, aconnection including resistance extending between one of said lineconductors of a connected telephone line and a return conductormaintained at a potential different from that pole of the source ofcurrent then connected to said line conductor, a polarized signalcontrolling electroinagnet having two windings associated with said linkcircuit, one of said windings being included'in circuit with said sourceof current and with said resistance when said line is connected withsaid link circuit, and included also in circuit with said source ofcurrent and with the line limbs of the telephone line and with thesecond winding when the circuit of the telephone liiie is closed at thesubstation, whereby a difierence in the relative polarization of thepoles of the said electroniagiiet in a certain direction is secured bycurrent over the former path to cause the display of its signal, andwhereby said difference in polarization is destroyed by current oversaid latand adapted to be bridged across the line circuits whenconnected for conversation, a

relay winding included in circuit between one of said line conductors ofa connected telephone line and a return conductor maintained at apotential diiierent from that sole of the source of current thenconnected to said line conductor, adapted to be energized from saidsource of current over a portion of the link circuit then connected withsaid line conductor to destroy the substation control of its associatedcall signal, a polarized signal controlling electromagnet associatedwith said link circuit, having a winding included in circuit with saidsource of current and with said relay winding when said line isconnected with said link circuit, whereby a difference in the relativepolarization of the poles of said electromagnet in a certain directionis secured to cause the display of its signal and a second winding forsaid electroniagne't in a circuit under the control of the substationswitch for destroying said relative difierence in polarization wherebysaid signal is efi aced.

25. A telephone exchange system including telephone lines extending to acentral ofiice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a

relay winding included in circuit between one of said line conductors ofa connected telephone line and a return conductor maintained at apotential different from that pole of the source of current thenconnected to said line conductor, adapted to be energized from-saidsource of current over a portion of the link circuit then connected withsaid line conductor to destroy the substation control of its associatedcall signal and a polarized signal controlling electroinagnet having twowindings associated with said link circuit, one of said windings beingadapted, when energized, to cause a difference in the relativepolarization of the poles of said electromagnet in a certain directionto cause the display of its signal, and the other of said windings beingadapted, when energized, to destroy said dilference of polarizationwhereby said signal is efiaced.

26. A telephone exchange system including telephone lines extending to acentral office, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a relay winding included in circuit betweenone of said line conductors of a connected telephone line and a returnconductor maintained at a potential different from that pole of thesource of current then connected to said line conductor, adapted to beenergized from said source of current over a portion of the link circuitthen connected with said line conductor to destroy the substationcontrol of its associated call signal and a polarized signal controllingelectromagnet having two windings associated with said link circuit, oneof said windings being included in circuit with said source of currentand with said relay winding when said line is connected with said linkcircuit, and included also in circuit with said source of current andwith the line limbs of the telephone line and wit-h the second windingwhen the circuit of the telephone line is closed at the substation,whereby a difference in the relative polarization of the poles of thesaid electromagnet in a certain direction is secured by current over theformer path to cause the display of its signal, and whereby saiddifference in polarization is destroyed by current over said latter pathto etl'ace said signal.

27. A telephone exchange system including telephone lines extending to acentral ofiice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a relatively high resistance connectionextending between one of said line conductors of a connected telephoneline and a return conductor, said return conductor being maintained at apotential different from that pole of the source of current thenconnected to said line conductor, said relatively high rellt sistanceconnection including a relay niagnet winding adapted to be energizedfrom said source of current over a portion of the link circuit thenconnected with said line to destroy the substation control of itsassociated call signal, a polarized signal controlling electroinagnetassociated with said link-circuit, having a winding included in circuitwith said source of current and with said relatively high resistanceconnection when said line is connected with said link circuit, whereby adifference in the relative polarization of the poles of saidelectroniagnet in a certain direction is secured to causethe display ofits signal and a second winding for said electroinagnet in a circuitunder the control of the substation switch for destroying said relativedifference in polarization whereby said signal is eii'aced. v

28. A telephone exchange system including telephone lines extending to acentral oflice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a

relatively high resistance connection extending between one of said lineconductors of a connected telephone line and a return conductor, saidreturn conductor being maintained at a potential different from thatpole of the source of current then connected to said line conductor,said relatively high resistance connection including a relay inagnetwinding adapted to be energized from said source of current over aportion of the link circuit then connected with said line to destroy thesubstation control of its associated call signal, and a polarized signalcontrolling electroinagnet having two windings associated with said linkcircuit, one of said windings being adapted, when energized, to cause adifference in the relative polarization of the poles of said electromagnet in a certain direction to cause the display of its signal, aiiclthe other of said windings being adapted, when energized, to

destroy said difference of polarization whereby said signal is efiaced.

25). A telephone exchange system including telephone lines extending toa central office, line conductors for extending said telephone lines tothe switchboard, spring acks associated with said line conductors at theswitchboard, calling signals associated with said lines and adapted 'tobe operated by current over said lines, l nk circuits for uniting saidlines for conversation, a source of current associated with said linkcircuits and adapted to be bridged across the line circuits whenconnected for conversation, a relatively high resistance connectionextending between one of said line conductors of a connected telephoneline and a return conductor, said return conductor being maintainedat apotential different from that pole of the source of current thenconnected to said line conductor, said relatively high resistanceconnection including a relay niagnet winding adapted to be energizedfrom said source of current over a portion of the link circuit thenconnected with said line to destroy the substation control of itsassociated call signal and a polarized signal controlling electromagnethaving two windings associated with said link circuit, one of saidclosed at the substation, whereby a difference in the relativepolarizationof the poles of the said 'electrornagiiet in a certaindirection is secured by current over the former path to cause thedisplay of its signal, and whereby said diflei'ence in polarization isdestroyed by current over said latter path to efface said signal.

'30. A telephone exchange system including telephone lines extending toa central office, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines "and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted 'to be bridged across the line circuits whenconnected -for conversation, a relay winding included in circuit betweenone of said line conductors of a connected telephone line and a returnconductor maintained at a potential different from that a polarizedsignal controlling electromagnetassociated with said link circuit,having a winding included in circuit with said source of current andwith said relay winding when said line is connected with said linkcircuit, whereby a difference in the relative polarization of the polesof said electroniagnet in a certain direction is secured to cause thedisplay of its signal, a second winding for said electroniagnet in acircuit under the control of the substation switch for destroying saidrelative difierence in polarization whereby said signal is efii'aced anda test circuit extending from said re turn conductor through a signalproducing device to the testing contact piece of a plug, whereby, whensaid testing contact piece of the plug is engaged with that contactpiece of a spring jack connected with said relay winding, a flow ofcurrent will result through said test circuit if another plug isinserted into another spring jack of the same line, and whereby, when noconnection exists with the line, no test indication will result.

31. A telephone exchange system includin telephone lines extending to acentral 0 cc, line conductors for extending said telephone lines to theswitchboard, spring jacks associated with said line conductors at theswitchboard, calling signals associated with said lines and adapted tobe operated by current over said lines, link circuits for unit ing saidlines for conversation, a source of current associated with said linkcircuits and adapted to be bridged across the line circuits whenconnected for conversation, a relay winding included in circuit betweenone of said line conductors of a connected telephone line and a returnconductor maintained at a potential different from that pole of thesource of current then connected to said line conductor, adapted to beenergized from said source of current over a portion of the link circuitthen connected with said line conductor to destroy the substationcontrol of its associated call signal, a polarized signal controllingelectroinagnet having two windings associated with said link circuit,one of said windings being adapted, when energized, to cause adifference in the relative polarization of the poles of saidelectromagnet in a certain direction to cause the display of its signal,and the other of said windings being adapted, when energized, to destroysaid difference of polarization whereby said signal is efiaced and atest circuit extending from said return conductor through a signalproducing device to the testing contact piece of a plug, whereby, whensaid testing contact piece of the plug is engaged with that contactpiece of a spring jack connected with said relay winding, a flow ofcurrent will result through said test circuit it another plug isinserted into another spring jack of the same line, and whereby, when noconnection exists with the line, no test indication will result.

32. A telephone exchange system including telephone lines extending to acentral oflice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a relay winding included in circuit betweenone of said line conductors of a connected telephone line and a returnconductor maintained at a potential ditlferent from that pole of thesource 01" current then connected to said line conductor, adapted to beenergized from said source of current over a portion of the link circuitthen connected with said line conductor to destroy the substationcontrol of its associated call signal, a polarized signal controllingelectromagnet having two windings associated with said link circuit, oneof said windings being included in circuit with said source of currentand with said relay winding when said line connected with said linkcircuit, and included also in circuit with said source of current andwith the line limbs of the telephone line and with the second windingwhen the circuit of the telephone line is closed at the substation,whereby a difference in the relative polarization of the poles of thesaid electromagnet in a certain direction is secured by current over theformer path to cause the display of its signal, and whereby saiddifference in polarization is destroyed by current over said latter pathto eitace said signal and a test circuit extending from said returnconductor through a signa producing device to the testing contact pieceof a plug, whereby, when said testing contact piece of the plug isengaged with that contact piece of a spring jack connected with saidrelay winding, a flow of current will result through said test circuitif an other plug is inserted into another spring jack of the same line,and whereby, when no connection exists with the line, no test indicationwill result.

A telephone exchange system including telephone lines extending to acentral oflice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, calling signals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a relatively high resistance connectionextending between one of said line conductors of a connected telephoneline and a return conductor, said return conductor being maintained at apotential different from that pole of the source of current thenconnected to said line conductor, said relatively high resistanceconnection including a relay magnet winding adapted to be energized fromsaid source of current over a portion of the link circuit then connectedwith said line to destroy the substation control of its associated callsignal, a polarized signal controlling electroinagnet associated Withsaldlink c1r-' cuit, having a winding included in circuit with saidsource of current and with said relatively high resistancev connectionwhen of the plug is engaged with that contact piece ot a spring jackconnected with said relatively high resistance connection, a flow ofcurrent will result through said test circuit if another plug isinserted into another spring jack of the same line, and whereby, when noconnection exists with [the line, no test indication Will result.

8d. A telephone exchange system including telephone lines extending to acentral oiiice, line conductors for extending said telephone lines tothe switchboard, spring jacks associated with said line conductors atthe switchboard, callingsig nals associated with said lines and adaptedto be operated by current over said lines, link circuits for unitingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a

relatively high resistance connectionextending between one of said lineconductors of a connected telephone lineand a return conductor, saidreturn conductor being main tained at a potential different from thatpole oi the source of current then connected to said line conductor,sald relatively high vresistance connection including a relay magnetwinding adapted to be energized :froin said source of current over a'portion'of the link circuit then connected with said line to destroythe substation control of its associated callsignal, a ,polarized signalcontrol-i ling electroinagnet having two windings associated withsaidlink circuit, one of said windings being adapted, when energized, to

cause a difference in the relative polarization of the poles-of saidelectromagnet in acertain direction to cause the display of its signal,and the other of said windings being adapted, when energized, to destroysaid {difference of polarization whereby-said signal is eitaced and a,test circuit extending from said return conductor through a signalproducing device to the testing contact piece of a plug, whereby, whensaid testing con- :tact piece of the plug is engaged with that contactpiece of va spring jack connected with said relatively high resistanceconnection, a flow of current willresult through said test circuit ifanother plug is inserted into another spring jack of the same line, andwhereby, when no connection exists with the line, no test indicationwill result.

35. A telephone exchange system including telephone lines extending to acentral oiiice, line conductors for extending said telephone lines tothe switchboard, spring acks associated with said line conductors .atthe switchboard, calling signals associated with said lines and adaptedto be operated by current-over said lines, link circuits for unit ingsaid lines for conversation, a source of current associated with saidlink circuits and adapted to be bridged across the line circuits whenconnected for conversation, a relatively high resistance connectionextending between one of said line conductors of a connected telephoneline and a return conductor, said return conductor being maintained atapotential different from that pole of the source of current thenconnected to said line conductor, said relatively high resistanceconnection including a relay magnet winding adapted to be energized fromsaid source of current over a portion of the link circuit then connectedwith said line to destroy ;the substation control of its associated callsignal, a polarized signal controlling electromagnet having two windingsassociated with said link circuit, one of said windingsbeing included incircuit with said source of current and with said relatively highresistance connection when said line is connected with said linkcircuit, and included also in circuit with said source of current andwith the line limbs of the telephone line and with the second windingwhen the circuit of the telephone line is closed-at the substation,whereby difi'erence in the relative polarization of the poles of thesaid electroinagnet in a certain direction is secured by current overthe former path toeause the display of its signahand whereby saiddifference in polarizat on is destroyed by current over said latter;path to eiface said signal and a test circuit extending from saidreturn conductor through a signalproducing device tothe testingcontactpiece of a plug, whereby, when said testing contact iiiece of'the plugisengaged with that contact piece of a spring, jack connected with saidrelatively high resistance connection, a flow 'of'current will resultthroughsaid test circuit if another plug is inserted into another springjack of the same line, and whereby, when no connection exists with theline, no test indication will result.

36. The combination, in a telephone exchange system, of a telephone-lineuniting a substation with the central office, a cordcircuit adapted tomake connection with said line, a polarized signal-controlling electromagnet having two opposing windings and responsive to current in onewinding only to cause the display of a signal, but not responsive tocurrent in both windings, a circuitfor one of said windings local to theexchange and under the control of the opera tor for causing theactuation of the electromagnet, and a switch at the substation includedin the circuit of the other winding when the line is switched forconversation.

37. A telephone system comprising a telephone line extending from asubstation to a central oiiice, a link-circuit for making connection tosaid line, a polarized two-windin signal-controlling electromagnetassociated with said link-circuit, means for displaying a signal inresponseto the one-winding energization of said electromagnet and forefi'acing said signal in response to the two-winding energizationthereof, a source of current, a resistance associated with saidtelephone line, means under the control of the operator for completing acircuit through one or" the windings of said signal-controllingelectromagnet and said resistance, and means under the control of thesubscriber, when the operator has completed said circuit, for completinga circuit including the other inding of said signal-controllingelectromagnet in parallelwith said resistance.

38. A telephone system comprising a telephone line extending from asubstation to a central ofiice, a linlocircuit for making connection tosaid line, a polarized two-winding signal-controlling electroniagnetassociated with said link-circuit, means for displaying a signal inresponse to the one-winding energization of said electromagnet and foreffacing said signal in response to the two-winding energizationthereof, a source of current, a line-signal associated with saidtelephone line, a signal-efiacing electromagnet for removing saidline-signal from the control of the subscriber, means under the controlof the operator for completing a circuit through one of the windings ofsaid signal-controlling electromagnet and the winding of saidsignal-effacing electromagnet, and means un der the control of thesubscriber, when the operator has completed said circuit, for completinga circuit including the other winding of said signal-controllingelectromagnet in parallel with the winding of said signaletfacingelectromagnet.

3 A telephone system comprising tele- Meet-w phone lines extending fromsubstations to a central oiiice, springjacks in which said linesterminate, a link-circuit and terminal plugs for connecting said linesfor conversation, a polarized two-winding signal-controllingelectromagnet associated with said link-circuit, means for displaying asignal in response to the one-winding energization of: saidelectromagnet and for eflfacing said signal in response to thetwo-winding energizalion thereof, a source of current, a resistanceassociated with each telephone line, means operative upon the connectionof said linkcircuitto a telephone line to close a circuit through one ofthe windings of said signalcontrolling electroinagnet and the saidresistance associated with said telephone line, means under the controlof the subscriber, when the operator has completed said circuit, forcompleting a circuit including the other winding of sa idsignal-controlling electromagnet in parallel with said resistance, atest circuit connected to one terminal of said resistance and extendingto the testing conact-piece of a terminal plug, and a signalproducingdevice associated with said test contact whereby, when said testingcontactpiece of the plug is engaged with the testing contact-piece of aspringjack associated with a disconnected line, no How of current willresult, and whereby, when said engagement is made with a springjack of aconnected line, a flow of current will result to cause the operation ofthe said signal-prmlucing device.

40. A telephone system comprising telephone lines extending fromsubstations to a central otiice, springjacks in which said linesterminate, a link-circuit and terminal plugs for connecting said linesfor conversation, a polarized two-winding signal-controllingelectromagnet associated with said link-circuit, means for displaying asignal in response to the one-winding energization of said electromagnetand vtor eitacing said signal in response to the two-windingencrgization thereof, a source of current, a line-signal associated witheach telephone line, a signalefiacing electromagnet for removing saidline-signal from the control of the subscriber, means operative upon theconnection of said link-circuit to a telephone line to close a circuitthrough one of the windings of said signal-- controlling electromagnetand the winding of the associated signal-eitacing electron'iagnet, meansunder the control of the subscriber, when the operator has completedsaid circuit, for completing a circuit including the other winding ofsaid signalcontrolling electromagnet in parallel with the winding ofsaid signal-efiiacing electromagnct, a test circuit connected to oneterminal oi said signal-eflacing elcctromagnet.

and extending to the testing contact-piece of a terminal plug, and asignal-producing device associated With said testcontact, Whereby whensaid testing contact-piece of the plug is engaged With the testingcontactpiece of a springjack associated With a disconnected line, noflow of current W111 result, and whereby When said engagement is madewith a springjack of a connected line,

HARRY Gr. VEBSTER.

Vvitnesses KEMPsTER B. MILLER, GRACE JMITCI-IELL.

Correction in Letters Patent No. 930,513.

It is hereby certified that in Letters Patent No. 930,513., grantedAugust 10, 1909, upon the application of Harry G. Webster, of Chicago,Illinois, for an improvement in TelephoneEXchange Systems, an errorappears in the printed specification requiring correction, as followsPage 7, line 1, after the Word current the Words and with Me Zine limbsq the telephone line should be inserted; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the ease in the Patent ()fiice.

Signed and sealed this 5th day of October, A. D., 1909.

[SEAL] C. C. BILLINGS,

Acting Commissioner 0 f Patents.

